London-listed Petra Diamonds has recovered five Type IIb blue diamonds of high quality, in terms of both their colour and clarity, at its Cullinan mine, in South Africa. The diamonds are also significant in terms of their size, weighing 25.75 ct, 21.25 ct, 17.57 ct, 11.42 ct and 9.61 ct, and are assessed to be individual stones and not originally part of one larger diamond.